Bottlenecks occur in a radio frequency transceiver as outphasing transmitters decompose a signal with amplitude and phase information A signal with amplitude and phase information may be decomposed into two constant-amplitude signals with only phase modulation.
FIG. 1 illustrates an embodiment of a decomposed radio frequency (RF) modulation. The RF modulation signal is decomposed into the constituent phase modulated signals. The desired RF signal 105 may be decomposed into two equal amplitude signals 110, 115 with time—varying phases The amplitude and phase of the RF signal is controlled through the time varying differential phase (ν) 120 and the common phase (φ) 125 respectively. Polar envelope elimination and restoration (EER) transmitters generate the same common phase signal (φ) 125 to drive the switching power amplifier. In this example, the amplitude information may be within the power amplifier by varying one or more of the supply, bias or number of unit devices.
FIG. 2 illustrates one embodiment of a common phase signal for a typical high data-rate radio frequency modulation, such as an orthogonal frequency-division multiplexing (OFDM) modulation. As shown in FIG. 2, a common phase signal 200 may be an unbounded random walk with discontinuities 205. Consequently, there exists a substantial need for unbounded phase modulation generated with high resolution and wide bandwidths in order to achieve a good error vector magnitude (EVM) and spectral purity.